1. Field of the Invention
The present invention relates to a deep-sea exploration multi-joint underwater robot system and a pressure housing. In particular, the present invention relates to a deep-sea exploration multi-joint underwater robot system, and a spherical glass pressure housing which includes a titanium band and is capable of withstanding a deep-sea water pressure and shielding built-in equipment from possible intrusion of seawater for allowing to transmit marine research data and underwater status data, wherein the system utilizes a multi-joint underwater robot which is configured to probe the sea floor with the minimum area to support, is capable of standing still with deep-sea legs, changing posture, walking and swimming, includes a depressor system for offsetting the weight of a primary underwater cable connected to a mothership, and is linked with a depressor by a secondary underwater cable.
2. Description of the Related Art
The sea holds 99% of space for the life on earth, 85% of which is deep sea and the exploration of around 1% is not made now.
Presently, only some limited countries including the United States, France, South Korea, Japan and Germany own unmanned submersibles capable of performing science exploration as deep as 6,000 m. All such unmanned deep-sea submersibles developed and operated to date are of screw-propelled submersible types.
In general, underwater robots can be classified by assignment into an autonomous unmanned submersible for principally exploring a wide range and a remote unmanned submersible or remotely-operated vehicle (ROV) to perform a high-precision operation in a relatively narrow area, where most of the underwater robots utilize the propeller as a propulsion device.
The propeller has been used for a long time as underwater propeller and its theory of propulsion mechanism is well established, and it has a higher efficiency in particular applications.
However, in a close on-the-spot survey of the deep sea, which consists of sediments, the propeller often has an issue of vortex flow to disturb the seabed, and a landing on the ocean floor for a close investigation requires a certain period of time until the mud subsides from tumult by the propeller flow, which renders the exploration difficult when an urgent observation is needed for a moving life and the like.
Other forms of undersea robots utilize a caterpillar or track and a plurality of legs rather than using the screw propulsion.
As part of biomimicry study, a obster robot has been developed [Joseph, A. (2004). “Underwater walking”, Arthropod Structure & Development Vol 33, pp 347-360.]. The study analyzed the kinematic structure of the lobster and its walking behavior, and implemented artificial muscle actuators, and a central controller based on command neuron.
Said robot focuses on research of biomimicry awareness and study of walking rather than the actual work. Underwater robot is also referred to as unmanned underwater vehicle (UUV), and roughly divided into autonomous unmanned vehicle (AUV) and remotely-operated vehicle (ROV).
Autonomous unmanned submersible is mainly used in scientific research and navigation over the region spanning a few hundred meters to several hundred kilometers. Most of the AUVs, which has been developed to date, have been used in scientific research and military purposes.
ROVs are utilized in the seabed surveys and precision work with the positional accuracy of a few tens of centimeters or less. The ROVs are utilized in a variety of works, including burying submarine cable, submarine pipeline, maintenance of seabed structures, and the like.
The application fields of the ROV can be summarized as follows.
First, the ROVs are used for exploration and salvage of sunken ships and the prevention of oil spill by sunken ships. Second, their applications are marine scientific research, and the exploration and development of marine resources. Third, ROVs are used for seabed structure installations, and for research support and maintenance. Fourth, they are utilized for military purposes, such as mine exploration, mine removal among others.
The ROVs for underwater missions get their mobility roughly in two forms.
First, screw propulsion is effective in the cruising types of AUVs, but it hardly achieves the stability of control in the ROVs that require operating precision. This is because the fluid force is non-linear acting on the ROV underwater and the thrust also involves strong inherent nonlinearity, such as a dead zone, delayed response, and saturation.
Second, track propulsion systems are difficult to run about an irregular seabed terrain and an area with obstacles and they have an inherent disadvantage from their running behavior that interferes with the seabed.
The seabed has ever-present constraints of a variety of obstracles such as sunken ships, fisheries, ropes and abandoned fishing nets, and constraints of seabed topography such as reef, soft ground and the like, which obstructs the track propulsion systems from running properly.
In addition, the track or caterpillar propulsion systems cannot match the intricacies of the application of in-situ survey that needs to be done with minimal interference in unobstructed environment, which is often the case with seafloor investigation.
In other words, the technical limitations or deficiencies of existing submarine operations can be summarized as follows.
When divers themselves participate in the operation, they are vulnerable to safety issues due to various risks, including decompression illness.
A diver's time underwater to work without decompression is limited to 30 minutes in 21-meter water depth, and to 5 minutes in 40-meter depth.
The ever-present danger of a variety of obstracles such as sunken ships, fisheries, ropes and abandoned fishing nets, and irregularities of seabed topography such as reef, soft ground and the like, interfere with the work of the divers, and pose life-threatening situations.
Underwater robots with the propeller or caterpillar propulsion systems inevitably interfere with the seafloor. The seafloor investigations often need to be carried out in environments uninterfered.
The screw-propelled ROVs for underwater operations have issues such as limited precise positioning capability that is needed for a precision exploration of slopes, rugged terrain, etc.
Conventional ROVs suffer from positional constraints in slope explorations that they need to be seated on the slope for properly conducting operations such as precision exploration and sampling. Conventional ROVs also need to move or hover at a constant altitude for continuous seafloor survey.
On the other hand, to prevent structural destruction due to deformation and stress under the internal pressure and external pressure conditions and to secure a structural safety under any circumstances, conventional pressure containers or housings are designed and fabricated pursuant to specific standards (for example, KS B 6750) by specifying the thickness, length, radii of an inner container and an outer container, welding condition, and molding conditions or the like.
Thus, the top priority of the structural safety requires a pressure housing to be made of a single continuum (i.e., integrated structure).
Accordingly, the present inventors have devised and realized a seamless or integral robot body including a frame free of separate coupling fixtures except for those exclusive for leg attachments and cylindrical pressure housings for the sake of structural safety of the system; and, as an accompaniment, multiple pressure housings for enabling a multi-joint underwater robot and a depressor to withstand the water pressure of the deep sea, for shielding built-in appratuses from seawater intrusion through waterproofing, and for allowing marine research data and underwater state data to be transmitted to a mothership.
In addition, the present inventors have devised a seamless integral robot body formation capable of maintaining an exact location even in the harsh subsea topographic exploration across slopes, rugged terrain, etc., with the free swimming ability for continuous seafloor survey without the passel to necessarily maintain a constant altitude, as well as including a frame free of separate coupling fixtures other than those exclusive for leg attachments and cylindrical pressure housings for the purpose of structural safety of the pressure housings.
As prior arts, there are Tanaka, T., Sakai, H., Akizono, J. (2004). “Design concept of a prototype amphibious walking robot for automated shore line survey work”, Oceans '04 MTS/IEEE Techno-Ocean '04, pp 834-839, JP 1996-334593 A and JP 4820804 B2.